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Gaskets are also used to cushion the glass on the interior and exterior faces of the glass.
The problem with gaskets is that they tend to be stretched during installation and will shrink back to their original length in a short time; they will also shrink with age and exposure to ultraviolet radiation. There is usually a gap in the gasket at the corners after shrinkage occurs. With a properly designed system the water that enters the system at the gasket corners will weep out through the snap cover weep holes.
To mitigate shrinkage of gaskets back from the corners the use of vulcanized corners and diagonally cut splices are recommended. Some curtain wall systems include condensation drainage provisions, such as condensate gutters, that are intended to collect and weep condensate from spandrel areas to the exterior; such condensate gutters and weeps are a violation of the air barrier of the curtain wall unless they are outboard of the backpan.
See discussion of back pans below. At the curtain wall perimeter, maintaining continuity of the air barrier reduces airflows around the curtain wall. Integration of perimeter flashings helps ensure watertight performance of the curtain wall and its connection to adjacent wall elements. Proper placement of insulation at the curtain wall perimeter reduces energy loss and potential condensation issues. Insulating the mullions in a spandrel area may lead to excessive condensation in cold climates unless it can also be assured that humid air from the interior will never come in contact with the mullions.
The spandrel area is typically not heated, thus the interior environment does not warm the mullions and offset the migration of the cold temperatures deep into the wall. In the vision area the interior heat helps to mitigate the cold and prevents condensation.
For this reason, do not insulate between the interior portion of mullions and adjacent wall construction either. Water penetration resistance is a function of glazing details see Glazing , frame construction and drainage details, weatherstripping and frame gaskets, interior sealants for operable windows, see Windows , and perimeter flashings and seals.
Water can enter the exterior wall system by means of five different forces: To mitigate water infiltration, all of these forces must be accounted for in the system design. Unlike discontinuous windows, which are smaller units and can rely to a high degree on sill flashings to capture frame corner leakage, curtain walls cover large expanses of wall without sill flashings at each glazed opening. Watertight frame corner construction and good glazing pocket drainage are critical for reliable water penetration resistance.
Key visual features of curtain walls are glazing appearance see Glazing and sightlines. Sightlines are defined as the visual profile of the vertical and horizontal mullions. The sightlines are a function of both the width and depth of the curtain wall frame. Lateral load resistance requirements wind loads, spans generally dictate frame depth.
Where narrow sightlines are desired, steel stiffeners inserted into the hollow frame of aluminum extrusions can help reduce frame depth. The acoustic performance of curtain walls is primarily a function of the glazing and internal seals to stop air leakage covered elsewhere. The sound attenuation capability of curtain walls can be improved by installing sound attenuating infill and by making construction as airtight as possible.
Incorporating different thicknesses of glass in an insulated glass unit will also help to mitigate exterior noise. This can be accomplished by increasing the thickness of one of the lites of glass or by incorporating a laminated layer of glass with a noise-reducing interlayer, typically a polyvinyl butyral or PVB. Back pans are metal sheets, usually aluminum or galvanized steel, that are attached and sealed to the curtain wall framing around the perimeter behind opaque areas of a curtain wall.
In cold climates insulation should be installed between the back pan and the exterior cladding in order to maintain the dew point outboard of the back pan so that the back pan acts as an air and vapor barrier. Back pans provide a second line of defense against water infiltration for areas of the curtain wall that are not visible from the interior and are difficult to access.
Water infiltration in opaque areas can continue for extended periods of time causing significant damage before being detected. Back pans also are to be preferred over foil vapor retarders in high performance and humidified buildings as convection currents short-circuiting the insulation can cause condensation, wetting and ultimately failure of these spandrel areas. Shadow box construction creates the appearance of depth behind a transparent lite of glass by incorporating a metal sheet into the curtain wall behind the lite. The metal sheet should be at least two inches behind the glass and may be painted or formed to create a texture, but reflective surfaces add the most visual depth to the wall.
Insulation should also be installed behind the shadow box if interior finishes prevent room air from contacting this area. The system should be designed to collect any condensation that may collect on the exterior side of the metal sheet and drain it back to the exterior. Shadow boxes present a variety of challenges related to venting the cavity behind the glass, that can allow dirt on surfaces difficult to clean, or sealing the cavity and risking excessive heat build-up.
Either way, the cavity may be at temperatures significantly above or below interior conditions with only thermally conductive aluminum between them. This can lead to condensation or surfaces so hot they can burn. Careful detailing can provide a method to thermally isolate the cavity from the interior.
An interior back pan behind the insulation is desirable as well, to avoid condensation on the metal shadow box from the interior. Curtain wall systems must transfer back to floor structure or intermediate framing both their own dead load plus any live loads, which consist primarily of positive and negative wind loads but might also include a snow load applied to large horizontal areas, seismic loads, maintenance loads and others.
Unfortunately, the curtain wall will likely demonstrate movement caused by thermal changes and wind significantly different than movement of the building structure. Therefore the connections to anchor the curtain wall must be designed to allow differential movement while resisting the loads applied.
The splice between the vertical mullions will also be designed to allow vertical movement while providing lateral resistance. In large areas of stick framed curtain wall, a split vertical mullion will be introduced periodically to allow thermal movement. Note that this movement slightly distorts the anchors at the vertical mullions.
Individual units of glass must accommodate the movement of the surrounding aluminum frame by sliding along glazing gaskets, distorting the gaskets or a combination of both. The movement of the glass within the frame and the movement forced in the anchors tend to induce additional stresses into a stick framed system.
Unitized curtain wall systems accommodate the differential movement between the structure and the thermal movement of the frame at the joints between each curtain wall unit. Because these units are frequently custom designed, the amount of movement to be accommodated can be carefully engineered into the system. Anchoring of unitized curtain wall typically consists of a proprietary assembly with three-way dimensional adjustability.
The anchors occur at each pair of vertical mullions along the edge of slab or spandrel beam. Frequently, unitized systems span from a horizontal stack joint located at approximately desk height up to the anchor at the floor line above and then cantilevering past the floor to the next horizontal stack joint. The stack joint is designed to resist lateral loads while the two floor anchors resist gravity and lateral loads.
One of the two floor anchors will allow movement in plane with the unitized system. Fire safing and smoke seal at gaps between the floor slab-edge and the back of the curtain wall are essential to compartmentalize between floors and slow down the passage of fire and combustion gases between floors. Laboratory-tested fire rated assemblies may be required in unsprinklered buildings by some codes as Perimeter Fire Containment Systems when the floor assemblies are required to be fire-resistance rated. The ratings of the Perimeter Fire Containment System must be equal to or greater than the floor rating.
These systems provide confidence that the materials used for perimeter containment remain in place for the specified duration of the required rating in a fire event. Fireman knock-out glazing panels are often required for venting and emergency access from the exterior. Knock-out panels are generally fully tempered glass to allow full fracturing of the panel into small pieces and relatively safe removal from the opening.
Knock-out panels are identified by a non-removable reflective dot typically two inches in diameter located in the lower corner of the glass and visible from the ground by the fire department. Buildings in cold climates have struggled throughout the ages with ice and snow formations that slide, fall, or get windblown from their roofs, ledges, and window sills, causing harm to people and damage to property below.
The curtain wall should be designed for accessibility for maintenance. Low-rise buildings can generally be accessed from the ground using equipment with articulated arms. For high rise construction the building should be designed for swing stage access for window cleaning, general maintenance, and repair work, like glass replacement. Davits and fall arrest safety tieback anchors should be provided on the roof and stabilization tie-offs provided on the face of the wall to comply with OSHA standards CFR Curtain wall leakage, both air and water, can contribute to IAQ problems by supplying liquid water and condensation moisture for mold growth.
This leakage can often remain concealed within the wall system and not become evident until concealed wall components experience significant deterioration and mold growth, requiring costly repairs. Glazing failures see Glazing. Repairs if feasible require significant disassembly of curtain wall.
If restoration of internal seals is not physically possible or not economically feasible, installation of exterior surface wet sealing at all glazing and frame joints is often performed. Failure of exposed gaskets and sealants , including perimeter sealants, from curtain wall movements thermal, structural , environmental degradation.
Repairs require exterior access. Aluminum frames are inherently corrosion resistant in many environments if anodized and properly sealed or painted with baked-on fluoropolymer paint. Aluminum frames are subject to deterioration of the coating and corrosion of aluminum in severe industrial, coastal environments and galvanic corrosion from contact with dissimilar metals.
Frame corner seals constructed using sealant are prone to debonding from prolonged contact with moisture and from thermal, structural, and transportation movements. Curtain walls and perimeter sealants require maintenance to maximize the service life of the curtain walls. Perimeter sealants, properly designed and installed, have a typical service life of 10 to 15 years although breaches are likely from day one. Removal and replacement of perimeter sealants requires meticulous surface preparation and proper detailing. Aluminum frames are generally painted or anodized. Factory applied fluoropolymer thermoset coatings have good resistance to environmental degradation and require only periodic cleaning.
Recoating with an air-dry fluoropolymer coating is possible but requires special surface preparation and is not as durable as the baked-on original coating. Anodized aluminum frames cannot be "re-anodized" in place, but can be cleaned and protected by proprietary clear coatings to improve appearance and durability. Exposed glazing seals and gaskets require inspection and maintenance to minimize water penetration, limit exposure of frame seals, and protect insulating glass seals from wetting. The best strategy for sustainability of curtain walls is to employ good design practices to ensure the durability maximum service life of the installation and to use systems that have a good thermal break and high R-value values as high as R-7 are possible with triple-glazed systems.
Also, the use of low-e and spectrally selective glass coatings can significantly reduce energy loads and improve comfort close to the wall. Aluminum and steel frames are typically recycled at the end of their service life. Recycling is less economical if the aluminum is contaminated with sealants, fractured glazing, etc. There is a limited market for salvaged steel and wood frames. Select a curtain wall with a demonstrated track record in similar applications and exposures.
Verifying track records may require significant research by the designer. ASTM E provides guidance. Review laboratory test results of systems or similar custom systems for air, water, and structural resistance, heat transmission, condensation resistance, sound transmission, and operability. Verify that tests pertain to the system under consideration and not a version of the system with the same product name but of different construction. Curtain wall design should start with the assumption that external glazing seals, perimeter sealant joints and curtain wall sills will leak.
The following summarizes recommended features:. In this system the glass and infill panels are installed from the exterior, typically against dry gaskets. The outer layer of gaskets is installed and the gaskets are compressed against the glass by the torque applied to fasteners securing a continuous pressure plate. The plate is later typically covered with a snap-on mullion cover. This system provides reasonable performance but is susceptible to leaks at corners or joints in dry gaskets. For improved performance four-sided gaskets can be fabricated at additional cost or wet sealants can be installed to provide a concealed interior toe bead or exposed interior cap beads.
Pressure plate glazing allows the easiest method to seal an air barrier from adjacent construction into the air barrier of curtain wall system. In this system the glass and infill panels are installed from the interior of the building, eliminating the need for substantial scaffolding and saving money. The frame is fixed and exterior dry gaskets are installed. Typically only the top interior mullion has a removable stop. The glass unit is slid into a deep glazing pocket on one jamb far enough to allow clearing the opposite jamb and is then slid back into the opposite glazing pocket and then dropped into the sill glazing pocket.
The removable interior stop is installed and finally an interior wedge gasket is forced in. Sometimes this method is called "jiggle" or "wiggle" glazing because of the manipulation necessary to get the glass into place. Performance is slightly reduced because dry metal to metal joints occur at the ends of the removable stop at a point that should properly be air and watertight. Wet sealant heel beads will improve performance and some systems include an extra gasket to form an air barrier seal.
Installation of spandrel panels may need to be installed from the exterior. In this system the glass or infill unit is adhered to the frame with a bead of silicone. Outer silicone weather seals supplement the structural seal. Unitized systems are frequently structural silicone glazed, especially if four-side SSG is desired. Two-sided SSG, with pressure plate glazing or wiggle glazing on the other two sides is acceptable to be field installed.
SSG is frequently mistakenly referred to as butt-glazing. True butt-glazing has no mullion or other back-up member behind the joint and relies solely on a sealant, typically silicone, between the glass units to provide a perfect barrier seal. Establish the required Condensation Resistance Factor CRF based on anticipated interior humidity and local climate data and select a curtain wall with an appropriate CRF.
Designers should be aware that the CRF is a weighted average number for a curtain wall assembly. The CRF does not give information about cold spots that could result in local condensation. Projects for which condensation control is a critical concern, such as high interior humidity buildings, require project-specific finite element analysis thermal modeling using software such as THERM.
Careful analysis and modeling of interior conditions is required to accurately estimate the interior temperature of the air at the inside surfaces of the glass and frame. Curtain walls that are set well outboard of perimeter heating elements will have air temperatures along their interior surface that are significantly lower than the design wintertime interior temperatures. Thermal modeling of the building interior using Computational Fluid Dynamics CFD software can help establish a reasonable estimate for air temperatures at the inside surfaces of the glass and frame.
These interior air temperatures are inputs for the thermal modeling software. Include lab mock-up thermal testing in addition to CFD modeling for analysis of project-specific conditions. Unusual or custom details, such as copings, deep sills, projected windows, spandrel areas and shadow box can dramatically alter performance. Use thermally broken or thermally improved aluminum frames for best performance. Special insulation provisions may be required where curtain walls project beyond adjacent cladding systems e.
Cheaper to produce, it allowed a greater diffusion of books. A number of Christian books were destroyed at the order of Diocletian in AD. During the turbulent periods of the invasions, it was the monasteries that conserved religious texts and certain works of Antiquity for the West.
But there would also be important copying centers in Byzantium. Despite this ambiguity, monasteries in the West and the Eastern Empire permitted the conservation of a certain number of secular texts, and several libraries were created: There were several libraries, but the survival of books often depended on political battles and ideologies, which sometimes entailed massive destruction of books or difficulties in production for example, the distribution of books during the Iconoclasm between and A long list of very old and surviving libraries that now form part of the Vatican Archives can be found in the Catholic Encyclopedia.
A very strong example of the early copying and conserving books is that of the Quran. Zayd collected all the available scriptures of the Quran scripted by different companions of Muhammad during his life. He compiled one scripture and got it verified by all the companions who had memorized the whole book while Muhammad was alive. Then this first official scripture was kept at the house of Hafsa, the wife of the Muhammad. By the time of the third caliph Uthmaan, the Islamic state had spread over a large portion of the known world. He ordered the preparation of the official copies of the first official scripture.
The copies were duly verified for accuracy. These copies were sent to each city of the caliphate so that further copies can be made locally with the perfect accuracy. To help preserve books and protect them from thieves, librarians would create chained libraries. Chained Libraries were books displayed next to each other to create a tight bond. This eliminated unauthorised removal of books. One of the earliest chained libraries was in England during the s.
Popular culture also has examples of chained libraries, such as in Harry Potter and the Philosopher's Stone by J. The scriptorium was the workroom of monk copyists; here, books were copied, decorated, rebound, and conserved. The armarius directed the work and played the role of librarian. The role of the copyist was multifaceted: Copies also allowed monks to learn texts and to perfect their religious education.
The relationship with the book thus defined itself according to an intellectual relationship with God. But if these copies were sometimes made for the monks themselves, there were also copies made on demand. The task of copying itself had several phases: The book therefore required a variety of competencies, which often made a manuscript a collective effort. The revival of cities in Europe would change the conditions of book production and extend its influence, and the monastic period of the book would come to an end.
This revival accompanied the intellectual renaissance of the period.
The Manuscript culture outside of the monastery developed in these university-cities in Europe in this time. It is around the first universities that new structures of production developed: The development of commerce and of the bourgeoisie brought with it a demand for specialized and general texts law, history, novels, etc. It is in this period that writing in the common vernacular developed courtly poetry, novels, etc. Commercial scriptoria became common, and the profession of book seller came into being, sometimes dealing internationally.
There is also the creation of royal libraries as in the case of Saint Louis and Charles V. Books were also collected in private libraries, which became more common in the 14th and 15th centuries. The use of paper diffused through Europe in the 14th century. This material, less expensive than parchment , came from China via the Arabs in Spain in the 11th and 12th centuries. It was used in particular for ordinary copies, while parchment was used for luxury editions. The invention of the moveable type on the printing press by Johann Fust, Peter Schoffer and Johannes Gutenberg around marks the entry of the book into the industrial age.
The Western book was no longer a single object, written or reproduced by request. The publication of a book became an enterprise, requiring capital for its realization and a market for its distribution. The cost of each individual book in a large edition was lowered enormously, which in turn increased the distribution of books.
The book in codex form and printed on paper, as we know it today, dates from the 15th century. Books printed before January 1, , are called incunables. The spreading of book printing all over Europe occurred relatively quickly, but most books were still printed in Latin. The spreading of the concept of printing books in the vernacular was a somewhat slower process. During the Enlightenment more books began to pour off European presses, creating an early form of information overload for many readers. Nowhere was this more the case than in Enlightenment Scotland, where students were exposed to a wide variety of books during their education.
The introduction of steam printing presses a little before , closely followed by new steam paper mills, constituted the two most major innovations. Together, they caused book prices to drop and the number of books to increase considerably. Numerous bibliographic features, like the positioning and formulation of titles and subtitles, were also affected by this new production method. New types of documents appeared later in the 19th century: Typewriters and eventually computer based word processors and printers let people print and put together their own documents.
Desktop publishing is common in the 21st century.
Among a series of developments that occurred in the s, the spread of digital multimedia, which encodes texts, images, animations, and sounds in a unique and simple form was notable for the book publishing industry. Hypertext further improved access to information. Finally, the internet lowered production and distribution costs. It is difficult to predict the future of the book in an era of fast-paced technological change.
A good deal of reference material, designed for direct access instead of sequential reading, as for example encyclopedias , exists less and less in the form of books and increasingly on the web. Leisure reading materials are increasingly published in e-reader formats. Although electronic books, or e-books, had limited success in the early years, and readers were resistant at the outset, the demand for books in this format has grown dramatically, primarily because of the popularity of e-reader devices and as the number of available titles in this format has increased.
Since the Amazon Kindle was released in , the e-book has become a digital phenomenon and many theorize that it will take over hardback and paper books in future. Many e-readers now support basic operating systems, which facilitate email and other simple functions. The iPad is the most obvious example of this trend, but even mobile phones can host e-reading software. Braille is a system of reading and writing through the use of the finger tips. Braille was developed as a system of efficient communication for blind and partially blind alike.
These characters are made with small raised dots in two columns similar to a modern domino piece to represent each letter.
Reading speed averages one hundred and twenty-five words per minute and can reach two hundred words per minute. Braille was named after its creator Louis Braille in in France. Braille stabbed himself in the eyes at the age of three with his father's leather working tools. Braille published his book "procedure for writing words, music, and plainsong in dots", in The code was developed to assign symbols to advanced mathematical notations and operations. The spoken book was originally created in the s to provide the blind and visually impaired with a medium to enjoy books.
In the American Foundation for the Blind created the first recordings of spoken books on vinyl records. Spoken books changed mediums in the s with the transition from vinyl records to cassette tapes. Compact discs reached more people and made it possible to listen to books in the car. Audiobooks could now be played in their entirety instead of being split onto multiple disks. The history of the book as an academic discipline studies the production, transmission, circulation and dissemination of text from antiquity to the present day.
Its scope includes the book as object, the history of ideas , history of religion , bibliography , conservation , curation and the future of the book. The history of the book came into existence in the latter half of the 20th century. It was fostered by William Ivins Jr. The Making of Typographic Man Another notable pioneer in the History of the Book is Robert Darnton. From Wikipedia, the free encyclopedia. This article has multiple issues. Please help improve it or discuss these issues on the talk page.
Learn how and when to remove these template messages. This article's lead section does not adequately summarize key points of its contents. Please consider expanding the lead to provide an accessible overview of all important aspects of the article. Please discuss this issue on the article's talk page. The examples and perspective in this article deal primarily with Western culture and do not represent a worldwide view of the subject. You may improve this article , discuss the issue on the talk page , or create a new article , as appropriate.
December Learn how and when to remove this template message. Manuscript culture and Illuminated manuscript. Rhetoric before and beyond the Greeks. Scribes, Script and Books. The Book Arts from Antiquity to the Renaissance. A social history of the Chinese book: Books and literati culture in late imperial China. Hong Kong University Press. An Introduction to Mass Communication". Asian Art Museum Education. Oxford, Oxford University Press. The New York Times. Archived from the original on June 29, Imperial Rome had a population of at least a million. Using a conservative estimate of literacy levels, there would have been more than , readers in the city.
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Tradition und Innovation , 4th ed. Retrieved 8 April The Irish Book in English, — The Edinburgh History of the Book in Scotland. The Future of the Book. University of California Press. This is Not the End of the Book: Or, new media and the myth of the disappearing medium".